Body Control Modules: Overview Chevrolet Venture I

DESCRIPTION

Vehicle can be equipped with one of 3 different Body Control Modules (BCM). Standard base models are equipped with BCM type 2 which controls all body control functions except Remote Keyless Entry (RKE) system and Central Theft Deterrent (CTD) anti-theft system. Models with RKE system are equipped with BCM type 3. Models with RKE system and CTD anti-theft system, or CTD anti-theft system only, are equipped with BCM type 4. To verify which BCM type is installed, see BCM TYPE VERIFICATION under SELF-DIAGNOSTIC SYSTEM

Body Control Module (BCM) performs multiple body control functions. The following vehicle systems or functions are controlled by BCM: audible warning and reminder chime functions, fasten seat belt warning indicator control, power door lock and automatic door lock functions, feature customization settings, interior light illumination, on-board diagnostics, Retained Accessory Power (RAP), RKE functions (if equipped) and Content Theft Deterrent (CTD) anit-theft system (if equipped). Body functions are controlled by output commands from BCM. BCM communicates with other control modules and components using class 2 serial data bus circuit. Class 2 serial data bus circuit is used to share information between other control modules and systems. BCM evaluates input information obtained from sensors and switches that are directly connected to BCM and controls various body systems by commanding an output on or off.

Body Control Module (BCM) controls many features and systems. By monitoring inputs signals which are hard wired directly to BCM and requests from other control modules connected to class 2 data bus circuit, BCM will send appropriate output commands to operate body features and components based on input signals and requests. BCM also retains feature customization settings for interior light illumination and power door lock operations specifically programmed for driver. Standard BCM (type 2) can control programmed interior and exterior lighting and power door locks when entering or exiting vehicle. Premium BCMs (type 3 or 4) can be programmed for optional equipment features. All models can be programmed to perform the following standard feature customization settings.

Modules are connected to class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among modules. When a module receives a message for a critical operating parameter, module records identification number of module which sent message for State Of Health (SOH) monitoring. A critical operating parameter is one which, when not received, requires that module use a default value for that parameter. When a module does not associate an identification number with at least one critical parameter within about five seconds of beginning serial data communication, DTC U1000 and/or U1255 is set. When more than one critical parameter does not have an identification number associated with it, DTC will only be reported once.

Conditions for running DTC U1000 and U1225, voltage supplied to affected module is within normal operating voltage range (about 9-16 volts). DTCs U1300, U1301 and U1305 are not currently set. Vehicle power mode (ignition switch position) requires serial data communication to occur. Conditions for setting these DTCs is that at least one critical operating parameter has not been associated with an identification number within about five seconds after beginning serial data communication. When DTC is stored in memory, modules use a default value for missing parameter(s).

Data messages are continuously exchanged between all control modules through class 2 serial data circuit. Data messages contain a 3-digit ID number to identify which control module sent message and are addressed to 3-digit ID number of control module(s) which data message is intended. State Of Health (SOH) messages are also sent every 2 seconds to immediately detect a loss of communication between control modules of class 2 serial data circuit. If a SOH message is not received by any or all control modules after 5 seconds, a loss of communication Diagnostic Trouble Code (DTC) will be stored by all affected control modules. Control module ID numbers for a failed control module or circuit can be identified by last 3 digits in DTC (DTC U1XXX) stored in memory.

Conditions for running DTC U1000-U1225, voltage supplied to affected module is in normal operating voltage range (about 9-16 volts). Diagnostic Trouble Codes (DTC) U1300, U1301 and U1305 are not set. Vehicle power mode (ignition switch position) requires serial data communication to occur. DTC will set when a learned identification number has not been sensed for last 5 seconds.

Data Link Connector (DLC) provides operating voltage for scan tool at terminal No. 16 (Orange wire) and ground at terminal No. 4 (Black wire). DLC provides serial 2 data signal data at terminal No. 2 (Purple wire) and signal ground at terminal No. 5 (Black wire). Scan tool should power up with ignition switch in LOCK position, although many modules will not communicate unless BCM detects ignition ON signal and send appropriate power mode message.

1. Check CIGAR/DLC (15-amp) fuse located in fuse block. If fuse is blown, go to next step. If fuse is okay, go to step 3.
2. Replace CIGAR/DLC (15-amp) fuse. Recheck fuse. If fuse is blown, repair short to ground in Orange wire between DLC connector terminal No. 16 and fuse block. See appropriate wiring diagram in «DATA LINK CONNECTORS»(/chevrolet/venture/i-1996-2005/remont/wiring-system-data-link-connectors-pwr-dist-grnd-dist/#data-link-connector-wiring-diagrams) article in WIRING DIAGRAMS. If fuse is okay, go to next step.
3. Check continuity between ground and DLC terminal No. 4 (Black wire). see scheme 4 If continuity exists, go to next step. If continuity does not exist, repair open or high resistance in Black wire between DLC and ground.
4. Check for poor terminal contact at DLC connector terminals No. 4 (Black wire) and No. 16 (Orange wire). Repair as necessary. If terminal contact is okay, go to next step.
5. Connect scan tool to another vehicle. If scan tool operates on another vehicle, check for poor connection between scan tool and DLC. If connection is okay, check for faulty scan tool. See scan tool manufactures instructions and repair as necessary. If scan tool does not communicate with another vehicle, check for faulty scan tool. See scan tool manufacturer's instructions and repair as necessary.

Modules connected to class 2 serial data circuit are monitored for communication during normal vehicle operation. Operating information and commands are exchanged between modules. Connecting scan tool to DLC allows communication with control modules for data messages, diagnostics and other information communications. DTCs may set due to symptom and during diagnostic procedures. Complete diagnostic procedure to ensure all DTCs are diagnosed and cleared from memory.

BCM detects that ignition is ON and sends appropriate power mode message to other modules. BCM must be connected to DLC for any other modules to communicate with scan tool. When class 2 serial data circuit is shorted to ground, DTC U1300 or U1305 will be set. When class 2 serial data circuit is shorted to power, DTC U1301 or U1305 will be set.

Scheme 1

Scheme 2

1. Connect scan tool to DLC. If scan tool powers up, go to next step. If scan tool does not power up, go to «SCAN TOOL DOES NOT POWER UP»(ref-9085-S03420620282000100700000).
2. Turn ignition switch to RUN position. Attempt to communicate with Powertrain Control Module (PCM), radio and remote CD player (if equipped), Electronic Brake Control Module (EBCM), Electronic Brake & Traction Control Module (EBTCM), Sensing and Diagnostic Module (SDM), Instrument Panel Cluster (IPC), Driver Information Display (DID) and Body Control Module (BCM). If scan tool communicates with any modules, go to next step. If scan tool does not communicate with any module, go to step 5.
3. Select DISPLAY DTCs for each module. Record each DTC, DTC status and module which stored DTC. If DTC U1300, U1301 or U1305 are stored, they should be ignored at this time. If any DTC between U1000 and U1255 exist, go to next step. If no DTCs between U1000 and U1255 exist, see check for short to power and short to ground in class 2 data bus circuits. If other DTCs exist, go to appropriate system starting point for related system.
4. If DTC U1000 or U1255 are only DTCs displayed in range specified in step 3, go to «DTC U1000 & DTC U1255: CLASS 2 COMMUNICATION MALFUNCTION»(ref-9085-S09114594452000101200000). If DTC U1000 or U1255 are not displayed in range specified in step 3, go to «DTC U1001-U1254: LOSS OF COMMUNICATION WITH XXX»(ref-9085-S01181985012000101000000).
5. Turn ignition switch to LOCK position. Disconnect scan tool. Inspect DLC connector terminals No. 2 (Purple wire) and No. 5 (Black wire) for poor terminal contact. Repair as necessary. Go to applicable diagnostic system check. See «TROUBLE SHOOTING»(ref-9085-S02717531962000100500000). If DLC terminal contact is okay, go to next step.
6. Check continuity between ground and DLC terminal No. 5 (Black wire). see scheme 4 If continuity exists, go to next step. If continuity does not exist, repair open or high resistance in Black wire. See «WIRING DIAGRAMS»(ref-9085-S31042073102000100400000).
7. Disconnect splice pack SP205. see scheme 5 Check for poor terminal contact at splice pack connector. Repair as necessary. Go to applicable diagnostic system check. See «TROUBLE SHOOTING»(ref-9085-S02717531962000100500000). If splice pack SP205 terminal contact is okay, go to next step.
8. Check continuity of class 2 data bus circuit (Purple wire) between DLC terminal No. 2 and SP205 terminal "A". see scheme 4and see scheme 5. If continuity exists, go to next step. If continuity does not exist, repair open or high resistance in Purple wire. See «WIRING DIAGRAMS»(ref-9085-S31042073102000100400000).
9. Using proper terminal adapter from Connector Test Adapter Kit (J 35616-A), connect jumper between splice pack SP205 harness connector terminals "A" (Purple wire) and terminal "B" (Dark Green wire). see scheme 5 Turn ignition switch to ON position. Attempt communication with Powertrain Control Module (PCM). If scan tool communicates with PCM, go to step 11. If scan tool does not communicate with PCM, go to next step.
10. Turn ignition switch to LOCK position. Disconnect PCM harness connector. Check for short to ground and short to power (with ignition switch in RUN position) in class 2 serial data circuit (Purple wire) between PCM connector terminal A5 and splice pack SP205. see scheme 5 Repair as necessary. See appropriate wiring diagram in «DATA LINK CONNECTORS»(/chevrolet/venture/i-1996-2005/remont/wiring-system-data-link-connectors-pwr-dist-grnd-dist/#data-link-connector-wiring-diagrams) article in WIRING DIAGRAMS. After repair, go to step 25. If circuit is okay, go to step 23.
11. Remove jumper wire from terminal "B" and connect jumper to terminal "F" (Dark Blue wire) of SP205 connector. Turn ignition switch to ON position. Attempt communication with Sensing and Diagnostic Module (SDM). If scan tool communicates with SDM, go to step 13. If scan tool does not communicate with SDM, go to next step.
12. Turn ignition switch to LOCK position. Disconnect SDM harness connector. Check for short to ground and short to power (with ignition switch in RUN position) in class 2 serial data circuit (Dark Blue wire) between splice pack SP205 harness connector terminal "F" and SDM harness connector terminal A5. see scheme 5 Repair as necessary. See appropriate wiring diagram in «DATA LINK CONNECTORS»(/chevrolet/venture/i-1996-2005/remont/wiring-system-data-link-connectors-pwr-dist-grnd-dist/#data-link-connector-wiring-diagrams) article in WIRING DIAGRAMS. After repair, go to step 25. If circuit is okay, go to step 23.
13. Disconnect jumper wire from splice pack SP205 harness connector terminal "F" (Dark Blue wire) and connect jumper wire to splice pack SP205 harness connector terminal "E" (Light Blue wire). see scheme 5 Turn ignition switch to ON position. Attempt communication with Electronic Brake Control Module (EBCM)/Electronic Brake and Traction Control Module (EBTCM). If scan tool communicates with EBCM/EBTCM, go to step 15. If scan tool does not communicate with EBCM/EBTCM, go to next step.
14. Turn ignition switch to LOCK position. Disconnect EBCM/EBTCM harness connector. (Scheme 1) Check for short to ground or short to power (with ignition switch in RUN position) in class 2 serial data circuit (Light Blue wire) between splice pack SP205 harness connector terminal "E" and EBCM/EBTCM connector terminal. See appropriate wiring diagram in «DATA LINK CONNECTORS»(/chevrolet/venture/i-1996-2005/remont/wiring-system-data-link-connectors-pwr-dist-grnd-dist/#data-link-connector-wiring-diagrams) article in WIRING DIAGRAMS. Repair as necessary. After repair, go to step 25. If circuit is okay, go to step 23.
15. Disconnect jumper wire from splice pack SP205 harness connector terminal "E" (Light Blue wire) and connect jumper wire to splice pack SP205 harness connector terminal "G" (Gray wire). see scheme 5 Turn ignition switch to ON position. Attempt communication with Instrument Panel Cluster (IPC) module. If scan tool communicates IPC module, go to step 17. If scan tool does not communicate with IPC module, go to next step.
16. Turn ignition switch to LOCK position. Disconnect IPC connectors. Check for short to ground and short to power (with ignition switch in RUN position) in class 2 serial data circuit (Orange wire) between splice pack SP205 and IPC module connector. Repair as necessary. See appropriate wiring diagram in «DATA LINK CONNECTORS»(/chevrolet/venture/i-1996-2005/remont/wiring-system-data-link-connectors-pwr-dist-grnd-dist/#data-link-connector-wiring-diagrams) article in WIRING DIAGRAMS. After repair, go to step 25. If circuit is okay, go to step 23.
17. Disconnect jumper wire from splice pack SP205 harness connector terminal "G" (Gray wire). Connect jumper wire to splice pack SP205 harness connector terminal "M" (Purple wire). see scheme 5 Turn ignition switch to ON position. Attempt communication with PASS-KEY(R) III (PK3) module. If scan tool communicates with PK3 module, go to step 19. If scan tool does not communicate with PK3 module, go to next step.
18. Turn ignition switch to LOCK position. Disconnect PASS-Key(R) III module harness connector. Check for short to ground and short to power (with ignition switch in RUN position) in class 2 serial data circuit (Purple wire) between splice pack SP205 in-line harness connector terminal "E" and PK3 module. see scheme 5 Repair as necessary. See appropriate wiring diagram in «DATA LINK CONNECTORS»(/chevrolet/venture/i-1996-2005/remont/wiring-system-data-link-connectors-pwr-dist-grnd-dist/#data-link-connector-wiring-diagrams) article in WIRING DIAGRAMS. After repair, go to step 25. If circuit is okay, go to step 23.
19. Disconnect jumper wire from splice pack SP205 harness connector terminal "M" (Purple wire) and connect jumper wire to splice pack SP205 harness connector terminal "K" (Purple wire). see scheme 5 Turn ignition switch to ON position. Attempt communication with Driver Information Display (DID). If scan tool communicates with DID, go to step 22. If scan tool does not communicate with DID, go to next step.
20. Disconnect jumper wire from splice pack SP205 harness connector terminal "K" (Purple wire) and connect jumper wire to splice pack SP205 harness connector terminal "D" (Orange wire). see scheme 5 Turn ignition switch to ON position. Attempt communication with radio. If scan tool communicates with radio, go to step 24. If scan tool does not communicate with radio, go to next step.
21. Turn ignition switch to LOCK position. Disconnect DID harness connector. Check for short to ground and short to power (with ignition switch in RUN position) in class 2 serial data circuit (Yellow wire) between splice pack SP205 harness connector terminal "K" and DID module harness connector terminal 15. Repair as necessary. See appropriate wiring diagram in «DATA LINK CONNECTORS»(/chevrolet/venture/i-1996-2005/remont/wiring-system-data-link-connectors-pwr-dist-grnd-dist/#data-link-connector-wiring-diagrams) article in WIRING DIAGRAMS. After repair, go to step 25. If circuit is okay, go to step 23.
22. Turn ignition switch to LOCK position. Disconnect radio. Turn ignition switch to ON position. Check class 2 data circuit (Yellow wire) between splice pack SP205 and radio for short to ground, then check for short to voltage. Repair Yellow wire as necessary. After repairs are complete, go to 25. If Yellow wire is okay, go to next step.
23. Check for poor terminal contact at class 2 serial data circuit of module that is not communicating. Repair as necessary. See «WIRING DIAGRAMS»(ref-9085-S31042073102000100400000). If terminal contact is okay, replace module in question. After repair, go to next step.
24. Replace any control module that does not communicate. Go to next step. NOTE: In the following step, scan tool may require a power up reset before communication will occur due to a short in class 2 serial data circuit. Ensure scan tool is off or is disconnected before performing test.
25. Reconnect all disconnected connectors and components. Install scan tool to DLC. Turn ignition switch to ON position. Wait 10 seconds. Select DISPLAY DTCs function for each module. Record and any loss of communication DTCs exist ("U" type DTCs) and DTC status. If no communication DTCs exist, go to next step. If any loss of communication DTCs exist and are current, go to appropriate «DIAGNOSTIC TEST»(ref-9085-S06559538752000100500000) in SELF-DIAGNOSTIC SYSTEM.

See also:
• EXTERIOR LIGHTS
• ILLUMINATION/INTERIOR LIGHTS
• POWER DISTRIBUTION
• DATA LINK CONNECTORS